Conventional cross-flow membrane modules used to separate gas or liquid mixtures in separations where the product is the retentate do not provide a means of separately capturing the fluid permeating through the membrane in the downstream, or product section of the module. Past a certain point in the module, which varies from application to application, this fluid has a higher concentration of the desired product than the incoming feed.
Various permeator module designs for fluid separation are described in the patent literature. U.S. Pat. No. 4,080,296 discloses a hollow fiber permeator comprising an elongated, ordered bundle of selectively permeable hollow fibers passing through a central tubesheet formed around a perforated feed tube containing a coaxial permeate conduit. U.S. Pat. No. 4,652,373 discloses a hollow fiber reverse osmosis permeator separtion unit comprising hollow fibers spirally wound on a hollow core creating a bundle of fiber lengths. Each of the fiber lengths pass through a tubesheet which is drilled with a hole pattern that cuts through all of the hollow fibers.
U.S. Pat. No. 4,666,469 discloses a hollow fiber membrane device comprising a plurality of hollow fiber membranes assemblies in a bundle about a feed flow distribution means with said membranes embedded in at least one tubesheet and the lumens of the fibers communicating through the tubesheet. A wrap of material envelopes a major portion of the longitudinal dimensions of the plurality of inner fibers assembled about the feed flow distribution means. The wrap serves to constrain the movement of the fibers within the wrap, but is formainous or contains other openings which permit passage of feed fluid through the inner fibers to the hollow fiber membranes. The permeate is collected in a header space of the device and removed at essentially the same concentration via two exit ports.
U.S. Pat. No. 4,119,417 discloses a gas separator comprising two membrane separation cells arranged in series. The first membrane separation cell comprises a feed pipe for conducting a gas mixture to a high pressure chamber of the first cell and a leadout pipe for drawing off either permeate or reject gas from the membrane located within the cell to a second separation cell. Either the permeate gas or reject gas from the second membrane cell is carried via a feedback pipe to the feed to the first separation cell.
U.S. Pat. No. 4,083,780 discloses a fluid purification system comprising a plurality of spiral wrap membrane elements placed in parallel within a pressure vessel. The spiral wrap membrane elements are designed to have product fluid passageways of short length to insure a low pressure drop in the passageways. The impurified fluid, i.e., that not collected as the main products, exits the vessel through a single fluid outlet.